Release Time

ATC uses an IFR release time2 in conjunction with traffic management procedures to separate departing aircraft from other traffic. For example, when controlling departures from an airport without a tower, the controller limits the departure release to one aircraft at any given time. Once that aircraft is airborne and radar identified, then the following aircraft may be released for departure, provided they meet the approved radar separation (3 miles laterally or 1,000 feet vertically) when the second aircraft comes airborne. Controllers must take aircraft performances into account when releasing successive departures, so that a B-747 HEAVY aircraft is not released immediately after a departing Cessna 172. Besides releasing fast aircraft before slow ones, another technique commonly used for successive departures is to have the first aircraft turn 30 to 40 degrees from runway heading after departure, and then have the second aircraft depart on a SID or runway heading. Use of these techniques is common practice when maximizing airport traffic capacity.